Experimental Investigation Of Grouting Polyurethane Into Sand Stratum

Sand formation is a special formation because of its poor self-stability,strong permeability,low adhesion between particles,it's often seen in Subway tunnel construction.The sand formation which subway tunnel in contains a lot of confined Water,it may easily lead piping,landslides and other accidents,we need to grout to plug the water or strengthen soil.Traditional inorganic grouting materials are easily diluted and broken up in the case of dynamic presence of water,but the polyurethane grouting material will react with water and coupled with the surrounding soil to solidify to plug the water and strengthen soil.It may release gases during the reaction and conducive to grouting.Research on polyurethane is a lot,but because of the toxicity problems and environmental issues,research on polyurethane grouting material which is suitable for metro tunnel construction is not specific enough.This paper attempts to make a polyurethane grouting material which is low pollution,low toxicity,and suitable subway tunnel construction,and test its basic performance,select the optimal formula,and test its sealing effect by the sand grouting experiment under hydrodynamic conditions.This research includes the following main contents:1.Select suitable raw materials and preparation methods and formulate two-component solvent-free polyurethane grouting material on the basis of understanding the basic polyurethane reaction and environmental principles.2.Use orthogonal experiment to draw each reagent addition amount of influence of the grouting material properties by the basic properties of the formulation within each group orthogonal test table such as the solidification time,the expansion ratio,the compression strength,the permeability,and the resultant solid content.Then determine the optimal formula.The final formula is that 1 parts of polyol,the same volume of a polyisocyanate,Organic amine catalyst content accounted for 0.3% of the polyol mass,organic tin catalyst content accounted for 1.6% of the polyol mass,agent chain extender content accounted for 0.6% of the polyol mass,content of the foam stabilizer accounted for 1.0% of the polyol mass.The slurry properties meet the requirements of plugging water.3.Analyze the toxicity of the optimal formula.And do the experiment that soak the consolidation of the mortar into water to compare its water samples with the original one,analyze the impact of the water quality by determining the loss of the specimen mass,the total solids of the water,comparing the different PH,and deserving the different electrolysis of water.4.Apply the optimal formula to the grouting simulation test.Make the two factors,water head height and grouting pressure,be adjustable,and determine grout diffusion distance,water plugging rate,sealing time and the changes of pore water pressure.Then comprehensively evaluate the effect of grouting at last.